1. Field of the Invention
The present invention relates to a communication system which accommodates a plurality of lines and a plurality of terminals, and matches a communication attribute of an incoming call or a held call with that of a terminal to respond to the call, and a call processing method.
2. Description of the Prior Art
When a data communication is performed through a communication system, and, for example, another incoming call is detected, the detected call is informed to a user as an in-communication incoming call via a data adapter connected to a data terminal. Furthermore, when information, associated with the incoming call, of a caller or a calling party who requests a new data communication is informed to the user, the user can determine whether the present communication should be maintained or the new incoming call should be preferentially processed, thus helping to improve response capabilities. More specifically, in some cases, the user wants to start the new communication while interrupting the present data communication depending on the caller's information. Thus, such a requirement of the user can be satisfied.
In a communication network having a function of sending caller information to a called party prior to the start of a communication, the above-mentioned operations are available. For example, in an ISDN which has been developed as an integrated digital service network, and is expected to provide various information communication services, caller information including a caller number is transmitted to a called party. Therefore, by utilizing this information, a user can be informed of the caller upon detection of an in-communication incoming call.
In a conventional communication system accommodating a plurality of lines and a plurality of terminals, when a given terminal responds to a new incoming call after a line in communication is held or is disconnected, or when the given terminal places a line on hold to perform a new communication and then responds to the held call, or responds to a held call which was held by another terminal, a user must change setup data to match a communication attribute requested by a call to be responded to with that of a terminal or a data adapter.
In a communication system of this type, there is no correlation between a display of an incoming call or a held call on a terminal and a communication capability or communication attribute of the terminal itself which makes the call display.
The communication attribute indicates information such as a transmission rate, a bit format (e.g., a stop bit, a data bit length, a parity bit type, and the like), a distinction between a synchronous/asynchronous communication, a character type, flow control information, a media type (e.g., voice/G3 FAX/G4 FAX/document information, and the like), and the like, and such information serves as agreement of a communication format with a communication station on the other end of a line or with a network for transmitting information in some cases.
The data adapter is an adapter used by a communication system such as an exchange system to accommodate data terminals and to exchange data. Some data adapters support a sequence such as V.25bis, X.21, or the like for automatically originating an outgoing call and answering an incoming call, and some other adapters can only match a data terminal with a modem pool in a system connected to the data terminal via an interface port and do not support the communication sequence itself at all. Furthermore, a section which supports data communication as a function of a stand-alone terminal is often called a data adapter.
In the above-mentioned prior art, a user of a communication system cannot determine a communication capability or a communication attribute of a terminal on the basis of an incoming call display or a held call display on the terminal. For this reason, the user often responds to the incoming call or held call using a wrong terminal which cannot be matched with a communication attribute requested by the incoming call or held call.
After the user responds to the incoming call or held call using the terminal which cannot be matched with the requested communication attribute, he or she often performs such a wasteful operation as looking for a terminal having a communication attribute which can respond to the incoming call or held call and transferring that call, or disconnecting the call because he or she cannot transfer the call.
More specifically, when a user responds to, e.g., an incoming call, he or she must temporarily hold or disconnect an ongoing call, and then change a communication attribute of the terminal and also setup data of a data adapter to which the terminal is connected. After the setup data are changed, the user then responds to the incoming call to cope with the above-mentioned in-communication incoming call. However, since a user must hold or disconnect a call, change setup data, and then respond to a call, such a sequence requires much labor and time. Even if a means capable of disconnecting and responding to a call in a series of operations is adopted, setup data of both the terminal and the data adapter must be changed as needed depending on operations of a user.
The prior art requires changing setup data of both the terminal and the data adapter, if necessary, in addition to operations to hold or disconnect a call and respond to the incoming call which are very troublesome for a user. Therefore, a caller may give up the call during these operations, and if the incoming call to be responded is stopped, a user cannot start a desired communication, and consequently fails to switch communications.
Setup change operations are done by a user may lead to an operation error or a setup error. When these errors occur, a communication often cannot be started, resulting in disadvantages and inconvenience.
In accordance with integration of communication services like in the ISDN and terminals tend to have hybrid functions, it becomes difficult for the prior art to cope with necessity of processing calls with various communication attributes on a single line or channel, and to cope with incoming calls and held calls having various communication attributes accordingly, resulting in a communication system very inconvenient for a user.